First impressions were that the Sumo is not a great substitute for a Kong - it's much less flexible (so less "chewwy"), and the hole in the base of the toy is much larger, so you need to be more creative in terms of what goes into the toy to make it challenging for the dog to get out. My smaller dog (Daisy) initially lost interest very quickly, as her snout was little enough to be able to shove part of her face into the hole and easily extract the treats within, and even the big dog figured out that just grabbing and shaking meant lots of treats everywhere
However, once I'd thought about it a bit, and put some longer chew strips folded inside the toy so the treats were wedged into place the sumo really came into its own. The pups threw that thing around the place like it was alive - they absolutely loved it! And the more vigorously they chased it, the more strangely it bounced and the more excited they got about chasing it about.
Cybi waiting for the sumo to start flying around the room, after a pause to refill it
So a worthwhile purchase, albeit a dismal failure for the original purpose, which was to keep them quiet while I was working. In fact, things got so excited that while on one particular skype call the guy on the other end wanted to know if I needed to "go break it up". Fortunately he is also a dog lover and has big dogs, so was pretty familiar with large, playful chaos, but still...embarrassing while trying to appear professional!
*it wasn't me, but I don't know who it was that caused it to end up inside my welly boot


